RU2350563C2 - Aluminium and hydrogen production plant - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: production plant includes fine-dispersed powdered aluminium and water mixer, reactor for water and aluminium reaction accompanied with generation of hydrogenous mixed gas and making aluminium oxidation products, as well as hydrogenous mixed gas and aluminium oxidation products exhaust device. Water and aluminium reactor is provided with mixer and suspension ultrasonic radiation source mounted in reactor.

EFFECT: higher processing rate.

1 dwg

Description

The invention relates to the chemical industry, in particular, to a device for producing hydrogen and aluminum hydroxide in a weak solution of alkali from aluminum metal by oxidation in an ultrasonic field.

Aluminum hydroxides are used in various industries as adsorbents, catalysts, etc. High-purity aluminum hydroxides are used in the electronic and optical industry in the form of a fine powder - as abrasive powders, in particular, for hard disks or magnetic heads, as well as for the production of raw materials for claims ceramics, synthetic rubies and sapphires for the optical and electronic industries, to increase the strength characteristics of concrete in critical construction.

The invention relates, in particular, to a method for producing aluminum hydroxides of boehmite form. The method allows to obtain hydrogen, which can be used for chemical production, metallurgy, autonomous energy supply based on hydrogen.

The main method for the industrial production of aluminum hydroxides is the Bayer process, and their subsequent drying and calcination lead to the production of aluminum oxides (Chemical Encyclopedia, ed. "Soviet Encyclopedia", M., 1988, v.1, s.213-214).

However, conventional methods for producing aluminum hydroxides do not provide a high purity product.

A known method of producing aluminum hydroxides in the form of a fine powder, which consists in mixing an aluminum compound, a precursor of α-aluminum and at least one of the compounds used as a seed material for crystals of aluminum hydroxide, followed by calcination in an atmosphere containing hydrogen chloride (EP No. 1262457, C01F 7/02, publ. 04.12.2002).

However, this method does not provide a material of the required purity and desired structure. In addition, the method of producing hydroxides in the form of gels is inconvenient in that its isolation is difficult to filter and, in addition, grinding or extrusion steps are necessary to obtain fine powders.

It seems that it is more convenient to obtain aluminum hydroxides by the interaction of aluminum metal with water, however, due to the formation of an oxide film on the surface of aluminum, its activity rapidly decreases. To prevent this phenomenon, various additives are used.

So, there are known methods for producing hydrogen, which consist in the interaction of metals, including aluminum with water (US No. 3348919, 423-657, publ. 10.24.1967, US No. 3985866, 423-657, publ. 12.10.1976). However, in these methods, in addition to aluminum, other metals are used - alkali, alkaline-earth metals, or alloys (EP No. 248960, С01В 3/086, publ. 12/16/1987).

In other methods (US No. 2958582, 423-627, publ. 01.10.1958, US No. 2958583, 423-627, publ. 01.10.1958) to obtain aluminum hydroxides and hydrogen, it is necessary to use additional substances that facilitate the interaction of the reactants, for example, catalytic amounts organic amines. The introduction of these substances makes it impossible to obtain pure aluminum hydroxide. The process of interaction of aluminum or its compounds and hydrogen is carried out in a facility that includes a reactor with a stirrer, where the starting reagents are introduced. The installation includes a heat exchanger, a separator and a filter for separating the resulting suspension of aluminum hydroxides with water.

Known (US No. 2758011, 423-627, publ. 07.08.1956) a method of producing alumina in the form of boehmite (γ-AlOOH), which consists in the interaction carried out in an autoclave, which load water and aluminum in the form of fine particles. The mixture is then heated to a temperature of 482-705 ° F (250-374 ° C), after which stirring is started at the same temperature under a pressure sufficient to maintain water in the liquid phase. The process is conducted for a time sufficient for the interaction of all aluminum; in the examples given, this time is about 4 hours. After all the aluminum has reacted, stirring is stopped, the autoclave with the reaction mixture is cooled and the resulting aluminum hydroxide is separated. The installation for carrying out the method includes a reactor with a stirrer, holes for introducing water and powdered aluminum, a sump, a condenser for receiving steam and gas. Carrying out such a method on an industrial scale is not technologically advanced due to its periodic mode; the method does not allow you to vary the form of the resulting product is aluminum hydroxide.

A known method of producing hydrogen, which consists in the fact that the metal-containing substances interact with water. The metal-containing substances are coated with a water-soluble polymer film before being fed to the reactor. The interaction is carried out in an aqueous medium, the parameters of which correspond to the parameters of its supercritical state, which makes it possible to carry out the process of layer-by-layer combustion of metal-containing substances with the evolution of hydrogen (RU No. 2165388, СВВ 3/10, publ. 04.07.2000).

Powdered aluminum can be used as metal-containing substances, and a solution of polyethylene oxide in dioxane or methyl alcohol can be used as a water-soluble polymer film. The pressure of the supercritical state of the aquatic environment is more than 22.12 MPa, and the temperature is more than 647.3 K (374 ° C). The method allows to obtain a hydrogen mixture of the composition: 96.1 vol.% Hydrogen, 3.9 vol.% Carbon monoxide; and carry out the regeneration of the feedstock. However, the form of the resulting aluminum hydroxide process is not boehmite.

An improved process for producing high-purity aluminum hydroxide [Al (OH) ₃ · 3H ₂ O] in the form of hydrargillite is known, which includes the steps of: (a) introducing solid, not powdered aluminum, preferably in the form of ingots, into hot water at about 70 ° C to obtain reaction mixture; (b) stirring this mixture for about 20 minutes; (c) introducing an alkali solid, preferably sodium hydroxide, into the mixture and heating it to a boiling point; (d) lowering the temperature to 75-80 ° C and stirring for 60 minutes; (e) lowering the temperature to room temperature; and (f) filtering the mixture, resulting in high purity aluminum hydroxide. This method uses an additional substance - sodium hydroxide, which contributes to the formation of impurities (US No. 5435986, C01F 7/02, publ. 25.07.1995).

A known method of producing hydroxides or oxides of aluminum and hydrogen from aluminum and distilled water, characterized in that from finely dispersed aluminum with a particle size of not more than 20 microns, a suspension of powdered aluminum in water is prepared at a ratio of Al: H ₂ O = 1: 4-16 weight.h ., which is continuously fed into a high-pressure reactor, where a suspension of powdered aluminum is sprayed with a droplet diameter of not more than 100 μm into water at a temperature of 220-900 ° C and a pressure of 20-40 MPa, with a ratio of suspension to water of 1: 50-100 weight. hours after exiting the high the pressure of the gas is fed into the condenser and hydrogen is removed from it, and aluminum hydroxide or aluminum oxide into the sump for suspension. In this case, boehmite aluminum hydroxide is obtained at a temperature of 250-350 ° C, a pressure of 32-35 MPa with a ratio of Al: H ₂ O = 1: 8-12 weight parts. (RU No. 2223221, C01F 7/42, СВВ 3/10, publ. 02/10/2004).

From the same source, a known installation for implementing the method, including a mixer, a reactor, a sedimentation tank for a suspension, a condenser. At the same time, the reactor is a high-pressure apparatus equipped with a nozzle for spraying a suspension of powdered aluminum in water to a droplet diameter of not more than 100 μm. To implement the method, first prepare a suspension of powdered aluminum (particle size up to 20 μm, preferably up to 5 μm) in water at a ratio of Al: H ₂ O = 1: 4-16 weight.h. This dispersion is fed into the reactor, where it is sprayed in water under a pressure of 20-40 MPa at a temperature of 220-900 ° C. It is necessary to provide fine spraying of the suspension — the size of the drops should be no more than 100 microns, while the ratio of suspension to water is 1: 50-100 parts by weight, with continuous removal of hydrogen and aluminum hydroxide.

This well-known decision was made as a prototype.

From the analysis of domestic and foreign publications it follows that the currently known methods do not ensure the completeness of aluminum oxidation with water and are inefficient. In addition, these methods use predominantly expensive ultrafine aluminum powders and activated aluminum alloys. The use of the latter to produce hydrogen is unpromising, since these are energy-consuming and low-productivity methods.

The present invention is directed to solving the technical problem of creating a plant for a continuous process, which allows to simultaneously produce hydrogen and aluminum hydroxides with high purity of the final product with the lowest possible energy consumption.

The technical result achieved in this case is to increase operational efficiency and productivity by ensuring the production of pure hydrogen and aluminum oxidation products while maintaining a safe temperature of the process mixture and eliminating the formation of an explosive mixture of hydrogen with oxygen.

The specified technical result is achieved by the fact that in the installation for the production of aluminum hydroxide and hydrogen, including a device for mixing finely divided aluminum and water powder, a reactor for the chemical interaction of water with aluminum, accompanied by the release of a hydrogen-containing gas mixture and the formation of aluminum oxidation products, as well as a device for removing hydrogen-containing gas mixture and aluminum oxidation products, the reactor for chemical interaction of water with aluminum is equipped with a mixing device m and a device for ultrasonic irradiation of the suspension located inside the reactor.

These features are significant and interconnected with the formation of a stable set of essential features sufficient to obtain the specified technical result.

The present invention is illustrated by a specific example, which, however, is not the only possible, but clearly demonstrates the possibility of achieving the above set of features of the required technical result.

In the drawing - a flow diagram of the production of aluminum hydroxide and hydrogen production.

In the framework of the present invention, a flow diagram of the production of aluminum hydroxide in a reactor by ultrasonic activation of aluminum metal powder in a weak alkali solution in a continuous mode is shown in the drawing, for a continuous method for producing hydrogen and nanosized aluminum hydroxide in a reactor by ultrasonic activation of aluminum metal powder in a weak alkali solution.

The apparatus for producing aluminum hydroxide and hydrogen includes a device for mixing finely divided aluminum and water powder in a predetermined proportion, from which this mixture is fed to a reactor for the chemical interaction of water with aluminum, accompanied by hydrogen evolution and the formation of aluminum oxidation products. The reactor for the chemical interaction of water with aluminum is made of low pressure with the function of mixing the rotation of the suspension inside the reactor and is equipped with an ultrasonic irradiation device for the suspension inside the reactor when it is stirred by rotation. Devices for removing the hydrogen-containing gas mixture and aluminum oxidation products form the transportation flows of finished products obtained in the reactor.

An apparatus for producing aluminum and hydrogen hydroxide includes a platform scale 1, a solvent reactor 2, a reactor 3, a condenser 4, a drying column 5, a clarifier 6, a filter 7 (or a centrifuge), an electric furnace 8 (dryer), and a ball mill 9, heat exchanger 10. Reactor 3 is equipped with a pressure sensor, a solution temperature sensor in the reactor, a metal sensor in the solution in the reactor, and a mixing device.

A solution of the electrolyte of a given concentration is prepared in a solvent reactor 2 by dissolving the amount of solid alkali measured by platform scales 1 in deionized water. The prepared solution is supplied to the reactor, at the same time, a water-aluminum suspension is fed into the reactor through the dispenser pump, the mixture of which is subjected to ultrasonic irradiation to disrupt the oxide film from the surface of aluminum particles and start its oxidation in reactor 3 with stirring and the temperature of the electrolyte inside this reactor is 65-70 ° FROM. The product resulting from chemical reactions, nanodispersed aluminum hydroxide, is washed from the electrolyte on filter 7. The first filtrate is returned to the solvent reactor 2 to prepare a new portion of the electrolyte solution. In order to reduce the load on the filter, easily coagulated sediments are separated from the supernatant in the clarifier-clarifier 6. The supernatant is used to prepare an electrolyte solution in reactor 2. Instead of filter 7, it is sometimes advisable to use a centrifuge. The necessary drying and calcining of the product is carried out in an electric furnace 8. If, as a result of heat treatment, the product loses its flowability, it is ground in a ball mill 9. Apparatus 7, 8 and 9 can be replaced by a spray dryer.

The evolved hydrogen passes through a condenser 4 to remove water vapor, the drying column 5 and is sent to the collector. The steam condensate is returned to the reactor. 3. To heat the water added to the reactor, a heat exchanger 10 is provided in the circuit.

When organizing the continuous production of aluminum hydroxide, water must be supplied to the jacket of the solvent reactor to heat the electrolyte to the required temperature. For this, the heat utilized in the jacket of the reactor 3 is used.

The developed hardware and technological scheme for the production of aluminum hydroxide can be easily mounted on the basis of existing electrochemical plants. The technology for producing hydrogen and aluminum hydroxides is that from a finely dispersed aluminum, with a particle size of not more than 20 microns, a suspension of powdered aluminum in water is prepared, which is continuously fed into the reactor through an ultrasonic irradiation unit. From the upper part of the reactor, the resulting steam-hydrogen mixture is fed to a condenser in which steam is condensed, and hydrogen is supplied to the overpass or consumer via the drying system. Aluminum hydroxide is removed from the bottom of the reactor to a clarifier clarifier. The technology for producing hydrogen and ultrafine aluminum hydroxide is based on a chemical reaction, presented according to the scheme.

Preferred indicators.

1. Simplicity, reliability and compactness of execution in comparison with analogues.

2. Low energy consumption per 1 m ³ N and 2 kg ALOOH: ultrasound - 500 W · h, pump - 500 W · h.

The novelty of the method lies in the fact that with a continuous controlled supply of an aqueous suspension of aluminum powder, its ultrasonic activation is carried out, where the chemical interaction of water with aluminum occurs, accompanied by the evolution of hydrogen and the formation of aluminum oxidation products (hydroxides). In general, the use of a combination of influencing factors in the developed method ensures the production of pure hydrogen, aluminum oxidation products, maintaining a safe temperature of the process mixture and eliminates the formation of an explosive mixture of hydrogen with oxygen.

The activation of aluminum is carried out according to the technology of preliminary processing of aluminum powders produced by the industry with ultrasound.

From the results of theoretical calculations and experimental studies it follows that when burning 1 kg of aluminum in aqueous media, along with thermal energy (17.1 MJ), a large amount of high-purity hydrogen (1.165 nm ³ ) is released and more than 2 kg of nanocrystalline aluminum hydroxides are formed, market the cost of which is $ 50-400 per kg.

This allows you to use this process to produce hydrogen in autonomous, high-performance and energy-efficient gas generating devices, including small-sized and autonomous gas-welding units.

When the generated hydrogen is burned in thermal and propulsion systems, the energy output (30.57 MJ / kg) exceeds the cost of regenerating the initial fuel from alumina (26.3 MJ / kg). Energy is provided during the complete regeneration of the starting components (aluminum and water) without emission of toxic components into the atmosphere.

The specific cost of 1 MJ of energy in the combustion of aluminum with its subsequent regeneration by electrolysis of aluminum oxide is significantly lower in comparison with the burning of gasolines and hydroelectricity.

The energy balance of the combustion and regeneration cycles provides a gain of about 16% of the energy due to the afterburning of the released hydrogen to water by atmospheric oxygen. Thus, with the complete regeneration of the starting reagents (aluminum and water), it is possible to autonomously provide thermal energy at a cost of 1 MJ - $ 0.0015, which is economically more profitable than burning hydrocarbon fuel ($ 0.007).

Aluminum energy technologies can be used in various power devices, as well as for the production of hydrogen and highly pure highly dispersed aluminum oxide, the market value of which for 1 kg is from $ 150 to $ 400 with the cost of the source aluminum 1,5-2 $ for 1 kg.

Thus, the present invention allows for the joint production of aluminum hydroxides of a given structure and hydrogen when carrying out the method in a continuous mode, with preliminary preparation of a suspension of powdered aluminum in water. The resulting method is characterized by non-waste, manufacturability and high productivity, as well as environmental safety.

Claims (1)

Installation for producing aluminum hydroxide and hydrogen, including a device for mixing finely divided aluminum and water powder, a reactor for the chemical interaction of water with aluminum, accompanied by the evolution of a hydrogen-containing gas mixture and the formation of aluminum oxidation products, as well as a device for removing the hydrogen-containing gas mixture and aluminum oxidation products, characterized the fact that the reactor for the chemical interaction of water with aluminum is equipped with a mixing device and an ultrasonic device radiation of the suspension located inside the reactor.